Sustainable concrete with seawater and corrosion resistant reinforcement: results of monitoring of corrosion behaviour

The use of seawater for mixing concrete in reinforced concrete structures is prohibited, since it can promote steel corrosion. However, the use of seawater would contribute to decrease the environmental impact of concrete, in particular in those coastal regions of the world where potable water is a precious resource. The project SEACON-INFRAVATION between University of Miami and Politecnico di Milano, with various industrial partners, aims at investigating the use of seawater for the construction of sustainable and durable reinforced concrete structures and infrastructures. Within the project, that included a vast campaign of laboratory tests, two demo projects – one in Italy and one in the US – were designed and executed with the aim of testing the use of seawater on-site and allowing long-term monitoring of the durability behavior. In Italy, a reinforced concrete culvert was built next to A1 motorway, close to Piacenza. The culvert collects the waters coming from the roadway that, during winter season, is subjected to de-icing salts; in addition, it is unsheltered from the rain and exposed to wetting and drying cycles. The culvert is divided into six segments, and each segment is representative of a given scenario in terms of type of concrete and type of reinforcement. Besides a reference segment, with carbon steel and chloride-free concrete, other segments were built using seawater concrete in combination with corrosion resistant reinforcement. Three types of corrosion resistant reinforcement were considered: an austenitic grade of stainless steel (1.4311), a duplex grade of stainless steel (1.4362) and GFRP. A concrete made with partial replacement of coarse aggregate with recycled asphalt pavement (RAP) was also considered. The corrosion conditions of the metallic reinforcements are monitored by means of potential measurements. The electrical resistivity of concrete is also monitored, and the evolution of carbonation and chloride penetration are periodically analysed on concrete cores taken from the culvert. This note presents the results that have been obtained during more than one year of monitoring of the corrosion conditions of the various types of reinforcement embedded in seawater concrete and compares them with results obtained in the laboratory